fix: ignore hh_client output during extension init

We run `hh_client` once on extension startup before starting the LSP
server because `hh_client --lsp` doesn't spawn `hh_server` if it's
not running already (facebook/hhvm#8548).
This can cause the extension to crash if there are a very large number
of errors, as the output of `hh_client` won't fit into `maxBuffer`.

Until we fix `hh_client --lsp`, let's simply instruct `hh_client`
to return no errors here because we don't actually care about the
output.

Author: mszabo-wikia

src/LSPHackTypeChecker.ts

@@ -46,6 +46,8 @@ export class LSPHackTypeChecker {
       }),
     );
 
+    // `hh_client --lsp` fails to spawn `hh_server` if not already running,
+    // so do an initial `hh_client` call to start the server if needed.
     await vscode.window.withProgress(
       {
         location: vscode.ProgressLocation.Window,

src/proxy.ts

@@ -19,11 +19,14 @@ export async function version(
   }
 }
 
+/** Run `hh_client` to start `hh_server` if needed. */
 export async function start(
   config: HackConfig,
   log: vscode.LogOutputChannel,
 ): Promise<string> {
-  return run(config, log, []);
+  // Ignore errors to avoid exceeding `maxBuffer` in case of many preexisting errors.
+  // We only run this command to ensure `hh_server` starts and don't care about the output.
+  return run(config, log, ["--max-errors", "0"]);
 }
 
 async function run(